Temporal changes in factors that contribute to the competitiveness of Florida beggarweed in peanuts were studied in 1986 and 1987. Florida beggarweed leaves were unifoliolate to the ninth node and trifoliolate thereafter. Peanuts grew taller than Florida beggarweed until the R-3 stage of peanuts, after which Florida beggarweed height increased logarithmically. Florida beggarweed branching was suppressed by the peanut canopy until the weed overtopped the peanuts. Florida beggarweed dry weight was reduced 80% by peanuts compared with Florida beggarweed grown alone. Peanuts reduced Florida beggarweed leaf area and canopy area. Percent light attenuation as a function of Florida beggarweed canopy area was described by the equation Y = lnX/25.5. Peanut yields in 60 cm of row on either side of a single Florida beggarweed plant were reduced 19%.

Field studies were conducted from 1985 to 1987 to evaluate postemergence herbicide systems with preemergence systems to control Texas panicum, Florida beggarweed, sicklepod, and pitted morningglory in peanuts. Adding paraquat at 0.14 kg ai/ha to postemergence herbicide systems reduced fresh weight of Florida beggarweed 92% (18% increase over the same systems without paraquat), sicklepod 95% (21% increase), and pitted morningglory 95% (11% increase). Herbicide systems containing paraquat improved peanut yields by 230 kg/ha and net returns by $52/ha over herbicide systems not containing paraquat. Fluazifop-P and sethoxydim systems reduced Texas panicum fresh weight (at least 96%) more than a preemergence system (92% reduction) that used benefin applied preplant incorporated and alachlor plus naptalam and dinoseb applied at cracking (GC) or a postemergence system that used alachlor and naptalam plus dinoseb GC and paraquat applied early postemergence (86% reduction). Systems containing fluazifop-P provided greater yields (4190 kg/ha) and net returns ($383/ha) than systems containing sethoxydim (4010 kg/ha, $305/ha) when averaged across all rates of application.